The present invention generally relates to methods and apparatus for accurately delivering precisely metered amounts of particulate material from dual station applicator wheels in a repetitive manner during high speed manufacture of particulate-filled articles of manufacture, and more particularly to precise and repetitive delivery of granular carbon from dual station applicator wheels into spaces presented during the manufacture of plug-space-plug cigarette filters.
Certain articles of manufacture such as carbon cigarette filters, individual-sized packets of granular food products or condiments, capsuled pharmaceuticals, ammunition and the like require repetitive placement of precisely metered charges of particulate matter at some location along the production-line procession of the articles. During high speed mass production of such articles it is difficult to achieve consistent accurate filling of the desired cavities with the granular particles. In the case of filling cigarette filter cavities with carbon, it is desirable to avoid excessive pulverization and scattering of the particulate material, while achieving as close to 100% fill of the cavities as possible.
U.S. Pat. No. 5,875,824, which is incorporated by reference herein in its entirety, discloses a method and apparatus for delivering predetermined amounts of material, wherein a single metering wheel receives discrete amounts of material from a supply chute, with the discrete amounts of material being transferred from the metering wheel to a transfer wheel, and from the transfer wheel into spaces along a filter rod. As a result of the transfer of particles from one wheel to another, the pockets for receiving the particulate material in the transfer wheel must be larger than the pockets in the metering wheel. This arrangement makes it difficult to achieve 100% fill of the cavities in the article receiving particulate material from the transfer wheel.
According to the ""824 patent, granular particles of carbon are drawn from a chute in communication with a reservoir into pockets on a rotating metering wheel. The rim of the metering wheel includes a plurality of equally spaced-apart pockets, each of which is defined by a radially directed, conical bore and a discrete screen at the base of the conical bore. The conical bore is convergent in the radially inward direction. A radially directed channel within the rim of the metering wheel communicates a backside of the screen with the interior of the metering wheel. A vacuum can be communicated from a stationary vacuum plenum in the interior of the metering wheel through the radial channel and screen such that any granular particles of the carbon that are adjacent the pocket in the metering wheel will be drawn into the conical bore of the pocket until it is filled.
An embodiment of the invention provides a method and apparatus for inserting granular particles of carbon or other materials into cavities defined in an article or plurality of articles, such as a cigarette filter rod, with the cavities being spaced at predetermined intervals. In the case of a cigarette filter rod, the cavities are spaced along the filter rod between filter components. In alternative embodiments the method and apparatus could include inserting particles or granules of other materials such as pharmaceuticals into cavities spaced along an article or in discrete articles such as individual capsules. Filling systems are provided adjacent upstream and downstream rotating applicator wheels each having spaced apart pockets that may be connected to a central stationary vacuum. The rotating wheels include pockets spaced around their outer surfaces, and a perforated metal band or screen which is clamped against the internal circumferential surface of the rotating wheels by a flexible segmented ring. The flexible segmented ring rotates with the wheel and has openings therethrough that coincide with the pockets around the outer surface of each rotating wheel. Each of the pockets is provided with a rectangular shape, extending inwardly until terminating at the perforated band or screen that is clamped against the inner circumference of the rotating wheel.
A stationary or rotatable vacuum plenum is provided in a drum radially inwardly from each rotating wheel and extending along an arc having a length coinciding with the distance between a point at which it is desired to provide vacuum to a pocket to draw in particles and a point at which it is desired to release the vacuum so that the particles can be released from the pocket into cavities traveling adjacent the periphery of the applicator wheels along a longitudinal path of travel.
The filling system adjacent to each rotating wheel includes a vertical drop chute with a height that is determined such that the particles accelerate under gravity through the drop chute and are traveling at approximately the surface speed of the rotating wheels when the particles enter the filling chamber. The filling chamber includes openings at the top to receive the particles from the vertical drop chute, at the bottom so that excess particles can drop out of the bottom of the filling chamber to be captured and recycled, and on the side of the filling chamber facing the rotating wheel. The side of the filling chamber opposite from the rotating wheel is provided with air inlets to allow cross air flow through the filling chamber and into the pockets of the rotating wheel. Each filling chamber can also be provided with optional deflector vanes to assist in deflecting the particles into the wheel pockets. As particles enter the top of the filling chamber from the vertical drop chute, cross air flow produced by the wheel vacuum and the inlets in the side of the filling chamber opposite from the wheel, direct the particles toward the wheel. The vacuum created by the stationary or rotatable internal vacuum plenum pulls the particles into the wheel pockets until the pockets are full. A scraper can be provided at the bottom of the filling chamber to scrap the outer surface of the wheel, thereby ensuring that each wheel pocket is accurately filled. A stationary air jet can also be provided inside the rotating wheel at a position adjacent the end of the vacuum plenum in the direction of rotation of the rotating wheel. The air jet directs a blast of air radially outwardly to assist in rapidly emptying each pocket of the rotating wheel as it rotates past the end of the vacuum plenum.
The cavities to be filled with the granules or particles are passed underneath each rotating applicator wheel and their movement is synchronized with the movement of the rotating wheels so that each cavity to be filled coincides with a pocket on the outer surface of each rotating wheel. A vacuum rail for conveying the article or articles having the cavities to be filled can also be provided. The material in which the cavities are formed can be porous material that allows the vacuum from the vacuum rail to create a negative pressure in the cavities. An example of such a porous material is the paper plug wrap used in forming cigarette filter rods. The vacuum rail can also be provided with separate chambers having higher and lower amounts of vacuum such that a chamber having the higher vacuum coincides with the cavity that is being filled with particles from the rotating wheel, while the other areas of the article coincide with the chambers having lower vacuum. The use of a high vacuum section in the vacuum rail at the point of particle transfer, and low vacuum at other points allows for quicker transfer of particles at the transfer point without having to adjust the rate at which the cavities are moved underneath the rotating wheel.
Both the upstream and downstream applicator wheels meter the particles and transfer the particles to cavities traveling underneath the wheels. The upstream wheel initially deposits a portion of the granular material into each cavity, and at the point of transfer from the upstream applicator wheel to the cavities, relatively high vacuum is applied to the cavities from below to draw in and affect transfer of the particulate material. The remaining portion of particulate material necessary for 100% cavity fill is transferred from the downstream applicator wheel to the partially filled cavities. At the location of the downstream applicator metering wheel relatively high vacuum is also applied at the point of transfer of the particulate material into the partially filled cavities, but such vacuum is applied at the upper sides of the cavity. Application of vacuum in this manner is instrumental in achieving approximately 100% fill of each cavity.